The present invention relates to abrasive articles and to a method of making and using abrasive articles. In particular, the present invention relates to abrasive articles comprising a UV-cured binder and filler.
Abrasive articles typically comprise a plurality of abrasive particles and a binder. There are a number of different types of abrasive articles on the market. These include coated abrasive products, bonded abrasive products and nonwoven abrasive products.
Coated abrasive products generally include a backing, abrasive particles, and at least one binder to hold the abrasive particles in an abrasive layer onto a major surface of the backing. The abrasive layer can be, for example, a single layer (e.g., a slurry layer) or multiple layers (e.g., make and size layers). The slurry layer may be applied as a slurry of abrasive particles in a binder precursor that is subsequently cured to form the binder. Such slurries of abrasive particles in a binder precursor and techniques for applying them are well known in the abrasive art. Make and size layers and methods for applying them are also well known in the abrasive art. In addition to adhering the abrasive particles to the backing, the make coat may also serve to seal the backing. The backing may be any suitable material including, but not limited to, cloth, polymeric film, fibre, woven fabric, nonwoven web, paper, or combinations thereof, or treated versions thereof. The abrasive particles can be present in one or more layers of the coated abrasive product.
Bonded abrasive products typically include a shaped mass of abrasive particles held together by an organic, metallic, or vitrified binder. Such shaped mass can be, for example, in the form of a wheel, such as a grinding wheel or cutoff wheel. The shaped mass can also be in the form, for example, of a honing stone, segment, mounted point, disc (e.g., double disc grinder) or other conventional bonded abrasive shape.
Nonwoven abrasive products typically include an open porous lofty polymer filament structure having abrasive particles distributed throughout the structure and adherently bonded therein by an organic binder. Examples of filaments include, but are not limited to, polyester fibers, polyamide fibers, and polyaramid fibers.
Abrasive articles typically include at least one binder (e.g., in make, size, and/or slurry layers of coated abrasive articles, or coated on a fiber web of nonwoven abrasive articles). Typically, binders are formed by curing (e.g., by thermal means, or by using electromagnetic or particulate radiation) one or more binder precursors. Useful binders and binder precursors may be inorganic or organic. Useful binder precursors include thermally curable resins and radiation curable resins, which may be cured, for example, thermally and/or by exposure to radiation. Exemplary organic binder precursors include glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, (e.g., an aminoplast resin having pendant α,β-unsaturated groups, acrylated urethane, acrylated epoxy, acrylated isocyanurate), acrylic resin, epoxy resin (including bis-maleimide and fluorene-modified epoxy resins), isocyanurate resin, as well as mixtures thereof.
Binders used to produce abrasive articles often contain fillers. Fillers are typically organic or inorganic particulates dispersed within the resin and may, for example, modify either the binder precursor or the properties of the cured binder, or both, and/or may simply, for example, be used to reduce cost. In coated abrasives, the fillers may be present, for example, to block pores and passages within the backing to reduce its porosity and provide a surface to which the maker coat will bond effectively. The addition of a filler, at least up to a certain extent, typically increases the hardness and toughness of the cured binder. Inorganic particulate filler commonly has an average particle size ranging from about 1 micrometer to about 100 micrometers, more preferably from about 5 to about 50 micrometers, and sometimes even from about 10 to about 25 micrometers. Depending on the ultimate use of the abrasive article, the filler typically has a specific gravity in the range of 1.5 to 4.5, and an average particle size of the filler will preferably be less than the average particle size of the abrasive particles.
Examples of useful fillers include: metal carbonates such as calcium carbonate (in the form of chalk, calcite, marl, travertine, marble or limestone), calcium magnesium carbonate, sodium carbonate, and magnesium carbonate; silicas such as quartz, glass beads, glass bubbles and glass fibers; silicates such as talc, clays, feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, and sodium silicate; metal sulfates such as calcium sulfate, barium sulfate, sodium sulfate, aluminium sodium sulfate, and aluminium sulfate; gypsum; vermiculite; wood flour; alumina trihydrate; carbon black; metal oxides such as calcium oxide (lime), aluminium oxide, titanium dioxide, alumina hydrate, alumina monohydrate; and metal sulfites such as calcium sulfite.
The use of UV-curable coating compositions in the preparation of coated abrasives is known. One of the problems associated with the use of UV-curable coating compositions in coated abrasives is that heavy filler loadings cause a shadowing effect and are inherently difficult to cure because the composition behind particles of filler tend to prevent penetration of UV-radiation throughout the depth of the coating. The problem is exacerbated in make coatings since the presence of the abrasive particles embedded in the partially cured coating also contributes to the shadowing effect.
WO97/36713, published Oct. 9, 1997, reports a coating composition suitable for the production of coated abrasives comprising a UV-polymerizable formulation and an alumina trihydrate filler that is substantially transparent to UV-light, wherein the amount of alumina trihydrate is said to be from 25 to 50% by volume of the coating composition.